became commonplace in the 1960s and 1970s as the world’s population grew to 3 and then 4 billion. World population passed 5 billion in 1987, 6 billion in 1999, and 7 billion early this decade; almost all this growth has occurred in the developing countries. Between 1945 and 2009, the growth in world population averaged a historically unprecedented rate of 1.6 percent per annum, twenty times faster than the estimated 0.08 percent between 1 C.E. And 1800.